<template>
    <div class="music-list">
      <div class="back" @click="back">
        <i class="icon-back"></i>
      </div>
      <h1 class="title" v-html="title"></h1>
      <div class="bg-image" :style="bgStyle" ref="bgImage">
        <div class="play-wrapper">
          <div class="play" v-show="songs.length > 0" ref="playButton" @click="random">
            <i class="icon-play"></i>
            <span class="text">随机播放全部</span>
          </div>
        </div>
        <div class="filter" ref="filter"></div>
      </div>
      <!--操作层-->
      <div class="bg-layer" ref="layer"></div>
      <!--操作层end-->
      <scroll :data="songs"
              :probeType="probeType"
              :listenScroll="listenScroll"
              @scroll="scroll"
              class="list"
              ref="list"
      >
        <div class="song-list-wrapper">
          <song-list :rank="rank" :songs="songs" @select="selectItem"></song-list>
        </div>
        <div class="loading-container" v-show="!songs.length">
          <loading></loading>
        </div>
      </scroll>
    </div>
</template>

<script>
  import Scroll from 'base/scroll/scroll'
  import SongList from 'base/song-list/song-list'
  import {prefixStyle} from "common/js/dom";
  import Loading from "base/loading/loading";
  import {mapActions} from 'vuex';
  import {playListMixn} from "common/js/mixin";
  // 使用prefixStyle
  const transform = prefixStyle('transform');
  const backdrop = prefixStyle('backdrop-filter');

  const RESERVED_HEIGHT = 40;
    export default {
      mixins: [playListMixn],
      name: "music-list",
      props: {
          bgImage: {
            type: String,
            default: ''
          },
          songs: {
            type: Array,
            default: []
          },
          title: {
            type: String,
            default: ''
          },
        rank: {
            type: Boolean,
          default: false
        }
      },
      data() {
          return {
            scrollY: 0
          }
      },
      computed: {
          // 计算属性得到 bgStyle css样式
          bgStyle() {
            return `background-image: url(${this.bgImage})`
          }
      },
      created() {
          this.probeType = 3;
          this.listenScroll = true
      },
      mounted() {
          // top 等于背景图高度
          // list 是一个Vue对象 需要拿它的DOM元素 加$el
          // 记录this.$refs.bgImage.clientHeight 值
          this.imageHeight = this.$refs.bgImage.clientHeight;
          // 记录最小滚动值 不滚动到顶部 加40
          this.minTranslateY = -this.imageHeight + RESERVED_HEIGHT
          this.$refs.list.$el.style.top = `${this.imageHeight}px`
      },
      methods: {
        handlePlayList(playlist) {
          const bottom = playlist.length > 0 ? '60px' : '';
          this.$refs.list.$el.style.bottom = bottom;
          this.$refs.list.refresh();
        },
          back() {
            this.$router.back()
          },
          scroll(pos) {
            this.scrollY = pos.y
          },
          selectItem(item,index) {
            this.selectPlay({
              list: this.songs,  // 推送所有的歌曲列表
              index
            })
          },
        random() {
            this.randomPlay({
              list: this.songs
            })
        },
        ...mapActions([
          'selectPlay',
          'randomPlay'
        ])
      },
      watch: {
          scrollY(newY) {
            // 设置滚动的最大值
            let translateY = Math.max(this.minTranslateY,newY);
            // 解决当滚动到一定高度时文字遮住图片
            let zImdex = 0;
            // 下拉图片放大
            let scale = 1;
            // 高斯模糊
            let blur = 0;
            // 放大比例
            const percent = Math.abs(newY/this.imageHeight);
            if (newY > 0) {
              scale = 1 + percent;
              zImdex = 10;
            } else {
              blur = Math.min(20 * percent, 20)
            }
            this.$refs.filter.style[backdrop] = `blur(${blur}px)`;
            this.$refs.layer.style[transform] = `translate3d(0,${translateY}px,0)`;
            // 当滚动到 顶部时
            if (newY < this.minTranslateY) {
              zImdex = 10;
              this.$refs.bgImage.style.paddingTop = 0;
              this.$refs.bgImage.style.height = `${RESERVED_HEIGHT}px`;
              this.$refs.playButton.style.display = `none`;
            } else {
              // 没有则回到最初
              this.$refs.bgImage.style.paddingTop = `70%`;
              this.$refs.bgImage.style.height = 0;
              this.$refs.playButton.style.display = `block`;
            }
            this.$refs.bgImage.style.zIndex = zImdex;
            this.$refs.bgImage.style[transform] = `scale(${scale})`;
          }
      },
      components: {
          Scroll,
          SongList,
          Loading
      }
    }
</script>

<style scoped lang="stylus" rel="stylesheet/stylus">
  @import "~common/stylus/variable"
  @import "~common/stylus/mixin"

  .music-list
    position: fixed
    z-index: 100
    top: 0
    left: 0
    bottom: 0
    right: 0
    background: $color-background
    .back
      position absolute
      top: 0
      left: 6px
      z-index: 50
      .icon-back
        display: block
        padding: 10px
        font-size: $font-size-large-x
        color: $color-theme
    .title
      position: absolute
      top: 0
      left: 10%
      z-index: 40
      width: 80%
      no-wrap()
      text-align: center
      line-height: 40px
      font-size: $font-size-large
      color: $color-text
    .bg-image
      position: relative
      width: 100%
      height: 0
      padding-top: 70%
      transform-origin: top
      background-size: cover
      .play-wrapper
        position: absolute
        bottom: 20px
        z-index: 50
        width: 100%
        .play
          box-sizing: border-box
          width: 135px
          padding: 7px 0
          margin: 0 auto
          text-align: center
          border: 1px solid $color-theme
          color: $color-theme
          border-radius: 100px
          font-size: 0
          .icon-play
            display: inline-block
            vertical-align: middle
            margin-right: 6px
            font-size: $font-size-medium-x
          .text
            display: inline-block
            vertical-align: middle
            font-size: $font-size-small
      .filter
        position: absolute
        top: 0
        left: 0
        width: 100%
        height: 100%
        background: rgba(7, 17, 27, 0.4)
    .bg-layer
      position: relative
      height: 100%
      background: $color-background
    .list
      position: fixed
      top: 0
      bottom: 0
      width: 100%
      /*overflow: hidden 列表可滚动上去*/
      background: $color-background
      .song-list-wrapper
        padding: 20px 30px
      .loading-container
        position: absolute
        width: 100%
        top: 50%
        transform: translateY(-50%)
</style>
